Vision disorders are the leading cause of handicapping conditions in childhood. Comprehensive eye examinations are recommended for preschool children because early detection increases the likelihood of effective treatment and allows for actions to decrease the negative impact of the disorders. However, less than 15% of all children receive an eye examination. And less than 22% of preschool children have some type of vision screening. Further, the methods for vision Screening vary tremendously and the effectiveness of the methods in appropriately identifying children has not been documented. The Vision In Preschoolers (VIP) Study is a multi-center, prospective clinical study to evaluate candidate screening tests for children aged 3 or 4 years. The primary goal of the VIP Study is to develop an effective and efficient battery of Screening tests that can be administered mainly by lay people and that have high sensitivity and specificity in identifying children in need of further evaluation for amblyopia, strabismus, and/or significant refractive error. To achieve these goals, a battery of screening tests will be administered at 5 VIP Participating Clinical Centers to at least 6,400 three- and four- year-old children enrolled at VIP affiliated Head Start sites. The battery will include tests chosen on the basis of their validity, design characteristics, and applicability to the preschool population. The battery will be administered primarily by lay people (Head Start parents) to maximize the availability of screeners, utilizes persons with a vested interest in benefitting children, and maximizes the applicability of this model to other communities. The screening battery will consist of the Massachusetts Visual Acuity Test (MassVAT), a form of the LEA symbols visual acuity test at distance, the Random Dot E (RDE) stereotest, and noncycloplegic autorefraction using a Nikon Retinomax. Every child who fails the screening, or is untestable, and a randomly selected subset of those children who pass the screening, at least 4,150, will undergo a comprehensive eye examination that will serve as the definitive method, or "gold standard", of detection of the target disorders.